The invention relates to the field of optical structures, and in particular to a technique for air gap formations.
Light manipulation is integral for optical communications, and includes functions such as filtering, switching, and light guiding. These functions are obtained by using various optical structures, such as filters, switches, and photonic band gaps. The degree of light manipulation depends on the index of refraction contrast between the materials used in the various optical structures.
Air gaps open the possibility for obtaining very high index of refraction contrast. The implementation of air gaps has been very difficult due to the difficulty in fabrication. Currently, air gaps are formed using bonding techniques and etching of a sacrificial layer. These techniques form structures that are open to water molecules or other impurities, which limit the performance of optical devices, and do not allow large gap formations. Furthermore, optical structures with large areas are not allowed using the previously described techniques, due to the stress formed in the optical structures.